This invention relates to an electronic control system, and more particularly to a control system which can selectively control the operation of a plurality of electrical devices energized from the same power lines.
Electric lights and other electrical apparatus are generally energized by means of power lines, and are interconnected to the power lines by switches. The switch is, of course, locally controlled. However, it is frequently desired to remotely control a number of electric lights, or other electrical devices, from a central control unit. For example, in offices, factories, hospitals, etc., it is necessary to have individual switches controlling the lights in each of the respective rooms. However, it is also important to have a central station which can selectively operate each of the switches to control the lights, or other electrical apparatus, connected to the outlets. Such systems are often installed for security purposes, accident prevention, for the assistance of handicapped or sick individuals, as well as for convenience.
At present, there are two schemes available for such remote control of lights and other electrical devices. In one method, a three-way switch is installed in place of the conventional switches and a separate cable is interconnected between each of the three-way switches and the central control unit. However, because these cables interconnect directly to the power lines through the three-way switches, it is necessary to utilize shielded or BX cable for these connections. Another method is to install separate relays at each of the switch boxes and utilize unshielded, low voltage wires instead of the BX cables to interconnect the individual relays with the central control unit.
However, with prior art devices, it is necessary to install individual lines or cables from each of the switches to the central unit. As a result, the cost in both time and material becomes exorbitant. It is necessary to drill holes through walls, ceilings, floors, etc. to lay and secure the BX cable or wire. Especially when the building is already completed, such installation is often too expensive to use.
Additionally, when a change, repair or replacement is necessary in the prior art conventional systems, it is again costly and necessary to open up walls, ceilings, etc. Furthermore, if one were to sell the house and want to remove the specially installed remote control system, again the cost would be expensive and the physical damage in removing the system would impair the property itself.
Since individual wires or cables must be installed, every time an additional light, or electrical device, is to be added on to the remote unit, specially skilled labor must be hired and special tools used to install the wires or cables and, as a result, it becomes prohibitive to individually add additional switches onto the system.